No joke intended at all!
There have been times when I ran out of fresh tumbling media (granulated walnut or corncob), and it was time to refill the tumbler.
Used media does wear out. It wears out by saturating with primer dust, grit, range dirt, and becomes glazed with bullet lubricant and case sizing residue. It feels gritty and no longer polishes brass....it just cleans and leaves a frosty finish.
Washing in a 5 gallon bucket with hot soapy water and a few squirts of dishwashing detergent works for me. Let it soak for a couple hours, agitate, and rinse a few times. You won;t believe how filthy dirty the rinse water comes out! Dry on old bath towels in direct sunlight.
The clean media works just like new! Some might think this is too much trouble to go to, but I've used the same media for a couple years now, and it seems to polish just as effectively as new stuff.
John